350 replies to this topic

[andy_leics22]

Very interesting Ensembles for London



Quite a lot of members going for below -5 from the 20th of Jan all the way to the end of the run. Some even hitting -10! It is still 50/50 though really, still some milder Ensembles in there but a lot more colder ones now than there were 2 days ago!

[Radiating Dendrite]

Zakos, on 16 January 2012 - 13:19 , said:

Yes everyone seems to think big of the met office. They're no better than anyone else. As long as that Russian high remains, it could at ANY time ridge over into scandi and at least deliver some snow to eastern areas. To completely ignore this possibility is simply wrong IMO.

Im still waiting for the BBQ summer to arrive....

To counter this, as long as the Jet remains active in the Atlantic it could block any westward progression of heights and leave us in mild mush.

The met-office have access to far more model output than we do on here, so to rubbish any forecast they make is rather foolish as it could be correct as they have been all winter so far to be fair.

The best thing is to concentrate on the model output upto 120hrs and just look for little trends and developments. Anything past this is gaga at the moment with the models really struggling to get a grip on what may occur.

[The PIT]

Ah well since everybody likes deep FI nice little storm in the ECM at t240. Sort of thing GFS tends to do. Pity we don't have a T264 as that chart would be interesting once the low passed through.

[Shunter]

<sup>Favourable Teleconnections response in todays update ( indeed one member reaches -6 on the AO index )

http://www.cpc.ncep....ex/ao.sprd2.gif</sup>

[Frosty039]

Anyway, there is no sign of anything significantly wintry showing up on the models for our part of the world in the next few weeks, as echoed by the experts, the models show a colder spell returning after the mild blip on wednesday, some wintry showers are possible later in the week and maybe into the weekend but then next week could be fairly average for the uk but at least the frosts should return after wednesday as it turns colder.

[Zakos]

AO forecast best so far this winter, solid support for a negative AO

.http://www.cpc.ncep....ndex_ensm.shtml

NAO not so great
http://www.cpc.ncep....index_ensm.html

But, it is looking roughly neutral, and we dont necasrily need the NAO to go negative for cold. It may even give a good battleground scenario...

[nick sussex]

I think the UKMO further outlook 6-15 days looks okay given the teleconnections. Block to the east, troughing near or over the UK and displaced Azores high.

However within that general pattern the weather you get depends on how far west/east this verifies. That outlook suggests a nw/se tilt to the jet and isn't as easy to model as a west/east zonal flow.

On top of this you have the matter of trough disruption, take the GFS 06hrs run at 192hrs as an example:



You can see there energy trying to get forced under the block, now looking at that chart I'd say theres a very good chance that we'd see some disruption with energy heading se, however as the GFS drops into the lower resolution it resolves this by pushing everything east.

The models are poor at handling these types of situations, especially in later timeframes.

So the outlook still remains to a large degree uncertain if those three factors at the top do indeed verify.

[Kent-Weather]

I don't post here ever to be honest but follow avidly, along with the posts of regular members for their knowledge and explaining charts. And for once I'm going to brave the scary waters!

I'm quite surprised how people are not spotting trends in the closer timescale and more so now that we are beginning to reach T+120. The model output (and more notably the stand off between GFS and ECM) has been purely fascinating to watch over the past 2 weeks overall. But now we are scratching the crumbs from T+120 we can start to endeavour our thoughts on a possible outcome.

My view is as that with low pressure suggested on FAX T120 over the North of Scotland (http://nwstatic.co.uk/fax/PPVO89.png), we can begin to focus on this being our main area of interest. What we also would need to know is where it is going of course..

GFS of recent days has promoted the TREND for low pressure to slide SE near to the E coast of the UK, and in recent days we have seen the all important jet stream become more aligned on a NW-SE angle (http://cdn.nwstatic..../102/hgt300.png).

Remember that GFS seemed to have an apparent massive error in previous days (hence the NOAA discussion sending out air recon seemingly to eliminate the error in spinup of GFS and thus sending it on a stand off with ECM - as we have seen), and now NOAA are working to resolve this, it's no wonder we are seeing something a little more settled. But until the error was resolved, ECM became the most likely outcome and was consistent in placing low pressure to the E or SE of the UK.

ECM 00z today: T+96 http://www.meteociel...M1-96.GIF?16-12
N. Hemisphere: http://www.meteociel...H1-96.GIF?16-12

And again, but T+120 http://www.meteociel...1-120.GIF?16-12
N. Hemisphere: http://www.meteociel...1-120.GIF?16-12

We still see that LP is likely to the N of the UK before sliding SE at T+120.

Lets factor in some other models/details shall we?

UKMO T+120 http://www.meteociel...20-21.GIF?16-06
A slower evolution I feel but a general theme (TREND) for LP to be situated N of the UK

UKMO T+144 http://www.meteociel...44-21.GIF?16-06
And then lower pressure further SE in a similar track.

Furthermore... as has already been posted.. The ensembles are all pretty good in their agreement in a drop for the 850hPa temperatures and also pressure out to the 20th

So to summarise. ECM was calling for low pressure to the E days while the GFS/ECM stand off was on going. We now see a blend of GFS/ECM and to some degree UKMO + FAX. Factoring in jet stream + ensembles, we can be pretty confident now surely of what's to happen for the rest of this week which may provide some better interest then we have seen in the past couple of weeks! We were looking at flat, zonal and horrible setups. Now we have something much closer to home so to speak. Wednesday we can then focus on snow potential and indeed if there is any potential.

My only advice would be to look for trends in the models themselves. This is one thing I learnt from this forum, the second was that in complete model contrast, a middle ground is the most likely answer. And I think all of the above writing has shown both learnings to be the best advice ever.

[JonMillar]

For those who wanted to compare equivalent runs these are 00z, and 06z runs for the past three days for the 20th, 21st and 22nd.

Attached Files

•  2012-01-20 Height 500hpa + SLP GFS 00z Model Output.xls   3.23MB   28 downloads
•  2012-01-21 Height 500hpa + SLP GFS 00z Model Output.xls   3.37MB   8 downloads
•  2012-01-22 Height 500hpa + SLP GFS 00z Model Output.xls   2.62MB   9 downloads
•  2012-01-20 Height 500hpa + SLP GFS 06z Model Output.xls   2.84MB   9 downloads
•  2012-01-21 Height 500hpa + SLP GFS 06z Model Output.xls   2.4MB   13 downloads
•  2012-01-22 Height 500hpa + SLP GFS 06z Model Output.xls   2.41MB   22 downloads

[weathermaster]

Review on the weather models this morning,

GFS

Lately it hasn't been performing good with a lot of outliers in the last few days and this morning it continues to struggle it has good support up to 96 hours but after this it completely loses it. All weather models at 120 hours (Saturday) show the rigding further East meanwhile the GFS has it more West. Also the GFS has a low pressure system just entering the Atlantic again no other models show anything like this at all. The GFS long term outlook shows we would have to wait until the end of the month for something cold but does show a blocking occur at the end of its run.

ECM

Still staying fairly consistent and has good support up to 120 hours. At 144 hours is a very important time at the moment because whatever happens here will affect our weather largely afterwards. The ECM like many other models show low pressure hanging about Greenland and Iceland all of them vary on its deepness and positioning. The ECM tries to make a blocking occur but with the low pressure around up there it isn't letting it happen. After this into the long term outlook the ECM shows a cold pool of air over the UK bringing unsettled and wintry weather.

GEM

It has good support up to 120 hours as well but after that like all models this morning takes a different route. It also tries to make a blocking occur at 144 hours and nearly gets there but with low pressure systems moving around the West of Greenland stops it from getting there. Its long range outlook isn't to bad not great for cold weather in the South but Northern parts could see cold weather.

NOGAPS

For the last few runs its been showing excellent charts and sort of agrees with the UKMO. It does try to make a better attempt of blocking although it looks like a toppler however it would give the UK a longer spell of cold weather.

UKMO

Continues to show great charts this morning and I believe its charts are looking the best of the day so far. It shows a good blocking occur with no low pressure systems around to stop it from breaking away. The UKMO continues to be consistent and refuses to back down. All we can hope for here is its right and the others follow.

Overall this morning we see good agreement up to 120 hours apart from the GFS which loses its mind by 96 hours. After this most of the models show a blocking trying to happen but with low pressure systems hanging about they knock it away. However the UKMO and NOGAPS seem confident on a blocking.

Today to Friday: Today staying settled for most and windy across the Western parts also still cold at times. Tuesday staying settled for the South but unsettled in the North. Wednesday will be unsettled for most with only the far South of England escaping the bad weather most of the UK will see wet and windy conditions with severe gales over Western and Northern Scotland. Thursday becoming more settled for all and turning colder across Scotland. Friday windy across Western parts and unsettled in the North with colder weather across Scotland and Northern England.

Saturday to Monday: Saturday will be windy again for Western parts meanwhile the North, East and South will see colder weather. Sunday looking unsettled mainly over the North and Northwest of Scotland where it will be windy. Staying cold over most of the country with Southern Ireland and South West England just missing out on the cold. Monday looks more settled for all and mainly Northern and Eastern parts seeing the best of the cold weather. The South West should start to see colder weather.

Monday and Beyond: Its hard to say what we can expect but the models show two routes. Either it remains cold and wintry until the end of the month and a bit unsettled at times or we go for a more settled period before seeing colder weather at the very end of the month.

[Paul]

Locking this shortly, ready for today's thread.